The Universal Serial Bus (USB) Specification was developed many years ago to facilitate connectivity between electronic devices. The bandwidth is improved from USB1.1 at 1.2 Mb/sec, 12 Mb/sec to USB2.0 at 480 Mb/sec and recently to USB3.0 at 5 Gb/sec. One of the reasons for the success of the USB interface is its backward compatibility from USB1.1/USB2.0 to the recent USB3.0. The user can plug in any USB device, no matter whether it is a USB1.1, USB2.0 or USB3.0 device, into the USB backward-compatible connector, and the system (or so-called host) will recognize the inserted USB device. More specifically, the USB 3.0 architecture, specified in the USB 3.0 Specification, Revision 1.0, Nov. 12, 2008, managed and disseminated by the USB Implementers Forum, Inc., includes highly desirable features over previous USB architectures, including the SuperSpeed (SS) protocol.
However, there are practical limits for the electrical cables (copper cables) used in USB1.1, USB2.0 or USB3.0 technology, such as speed and length due to electro-magnetic interference (EMI) and other issues. However, optical technology, which is used extensively in data centers and telecommunications, does not have these limitations since it transmits data using light instead of electricity and is promoted for the next generation of USB Specification. That is, the electrical cable is replaced with an optical cable so that the transfer speed is upgraded to 10 Gb/sec or even up to 100 Gb/sec in the next decade and beyond. When USB technology advances to an optical solution (USB next generation), there will be a backward compatibility issue due to the fact that most electrical devices integrated with USB connectors presently support electrical signal transmission rather than optical signal transmission.
Consequently, the inventor has observed that it is highly desirable to provide solutions to offer compatibility among different speeds of USB devices from USB1.1 at 1.2 Mb/sec, 12 Mb/sec, USB2.0 at 480 Mb/sec, or USB3.0 at 5 Gb/sec, to optical USB at 10 Gb/sec or higher.